U.S. Secret Service agents, aided by Baltimore police, have broken up a sophisticated counterfeiting operation that one official says had the potential of being the largest of its kind in Baltimore history.

Joseph R. Coppola, special agent in charge of the Secret Service office in Baltimore, said the alleged counterfeiters were gearing up to print $50 million in U.S. $50 and $100 bills, and foreign currency as well, for distribution in European and Middle Eastern countries.

"We find a counterfeiting plant every now and then," Coppola said, "but to my knowledge we have never had one of this size in Baltimore. The last one was a ma-and-pa operation."

Federal agents arrested three suspects, two Egyptian immigrants and a Baltimorean, and filed counterfeiting conspiracy charges against them about the time a search warrant was executed at the alleged printing plant, a warehouse in the 1100 block of E. Lombard St.

Coppola said the Secret Service seized about $20,000 worth of printing equipment, printing plates secreted in a ceiling, negatives, ink and high-quality, red-content paper in the warehouse raid.

The agents also seized negatives which contained copies of the U.S. Treasury seal that is printed on Federal Reserve notes.

"They had begun printing, and were going through the painstaking process of simulating red and blue threads" on the paper to make the currency appear genuine, Coppola said. "Not all counterfeiters take the time to do that."

Two of the suspects, Mustafa Mohamed Salama, 34, of the 6900 block of German Hill Road, Dundalk, and Mohamed Sedky Mohamed, 30, of the 700 block of Ponca St., were held yesterday pending detention hearings late today in U.S. District Court in Baltimore.

Magistrate Judge Deborah K. Chasanow continued an initial appearance for the other suspect, Richard Marlow Gore, 59, of the 1200 block of Carroll St., after he exhibited apparent symptoms of alcohol withdrawal in court. Gore was taken to a hospital for treatment, said prosecutor Maury Epner.

Gore, who allegedly boasted to Secret Service agents that he was a counterfeiter after his arrest, was convicted of counterfeiting charges here in 1983 and was sentenced to five years in federal prison.

"Our intelligence information is, the other suspects knew that and sought him out," Coppola said.

According to an affidavit filed in court, the Secret Service learned of the alleged scheme May 21, when Gore allegedly tried to purchase green ink, of the shade used on U.S. currency, at a local printing supply store in East Baltimore.

The affidavit said Gore showed a $50 bill to employees at the John H. Burke Co., pointed to the green serial number on it, and told them, "This is the color I need."

A store official called the Secret Service, but by the time an agent arrived there the man had gone.

While the agent was there, however, a woman called and identified herself as the man's wife. Agent Jeffrey W. Irvine spoke with the woman on the telephone and identified himself as a customer service representative of the Burke company.

The woman said she and her husband wanted to buy ink that was "green, apple green, like the green serial numbers of money," according to the affidavit.

Over the next three weeks, the Secret Service identified the woman as Estell Wienecke, of the 200 block of S. Highland Ave.; identified her alleged husband as Gore, a known counterfeiter; and identified Salama after he ordered more than $15,000 worth of graphic-arts equipment at Western Newspaper Litho Supply Co. and had it delivered to the Lombart Street warehouse, the affidavit said.

Another undercover Secret Service agent delivered the equipment and allegedly helped Mustafa install it in the warehouse. Secret Service agents installed three closed-circuit television cameras in the warehouse and videotaped the suspects at work there over the next several weeks, the affidavit said.

Salama, who exports cars to Egypt and other Middle Eastern countries, rented the warehouse and equipped it with a printing press, a large industrial camera, plate maker, light table, numbering machine and paper cutter, Coppola said.

The three suspects allegedly had been working since late May to produce first-rate counterfeit currency.

Coppola said the ring planned to print $50 million for distribution overseas, and "were planning on fooling with the currencies of other nations" as well.

The agents found "some images" which indicated that the ring intended to print Saudi Arabian money, Coppola said. He declined to identify other countries that he said the three men intended to victimize.

Coppola also said the investigation is continuing, and that other arrests are expected.